OPTIMUM MATING SYSTEMS FOR THE MYOSTATIN LOCUS IN CATTLE

Authors: Keele, John; Fahrenkrug, Scott

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: Inactive terms of the myostatin gene result in increased muscularity, increased yield of closely trimmed retail product, reduced fat content, increased lean growth efficiency, reduced quality grade, increased birth weight and increased dystocia in cattle. Even though inactive myostatin reduces quality grade or marbling, there is no decrease in meat tenderness. .It may be possible to use mating systems to make the most of the advantage of inactive myostatin while minimizing disadvantages. The objective of this study was to characterize all mating systems for genotypes at myostatin that potentially maximize profit and evaluate the impact of economic variables on comparisons among mating systems. Unfortunately, a single mating system utilizing genotypes at myostatin is not expected to generate maximum profit in all circumstances because of variation in economic variables and biological parameters. Despite this, it is possible eto define ranges in economic variables that are consistent with a particular mating system generating maximum profit. These ranges in economic variables when compared to market price forecasts provide a basis for decisions. Profitable use of inactive myostatin depends on the existence of a market in which beef is priced per unit of closely trimmed choice retail product. Marketing cattle based on conventional yield and quality grades does not favor use of inactive myostatin. To make use of between breed heterosis, crossbreeding systems can be implemented on top of myostatin mating systems without any increase in complexity over conventional systems.

Technical Abstract: Inactive myostatin (1 or 2 copies) results in increased muscularity, increased yield of closely trimmed retail product, reduced fat content, increased lean growth efficiency, reduced quality grade, increased birth weight and increased dystocia. Even though 1 or 2 copies of inactive myostatin reduces quality grade or marbling when compared to 0 copies, there is no decrease in meat tenderness. The objective of this study was to characterize all mating systems (MS) for genotypes at myostatin that potentially maximize profit and evaluate the impact of economic variables on comparisons among mating systems. Comparison of profit among myostatin mating systems depends on price per unit of choice retail product, price spread between choice and standard, price spread between choice and select, cost of an assisted calving and cost of genotyping. Average profit per cow is a linear function of economic variables with linear coefficients that depend on biological parameters. Because of variation in both economic variables and biological parameters, a single mating system is not expected to universally maximize profit. The linear profit equation can be used to define ranges in economic variables which are consistent with a particular MS generating more profit than others. Profitable use of inactive myostatin depends on the existence of markets where beef is priced per unit of closely trimmed retail product. Cross-breeding systems designed to make use of heterosis can be implemented on top of mating systems among myostatin genotypes without increased complexity compared to conventional systems. The red/black locus can be used to reduce the number of breeding pastures required.